• Topics: Agronomy | Langeland, Kenneth | Overholt, William A | Natural Area Weeds | Solanaceae (taxonomic family) | Invasive Weeds | Tropical Soda Apple

Natural Area Weeds: Invasive Solanum spp. in Florida¹

Introduction

The Florida Exotic Pest Plant Council's (FLEPPC) 2007 List of Invasive Plant Species includes two Category I and three Category II Solanum species (Solanaceae) (FLEPPC 2007). Category I Solanum species identified by the Council are S. tampicense Dunal (wetland nightshade, aquatic soda apple) and S. viarum Dunal (tropical soda apple). Category II Solanum species identified by the Council are the following: S. diphyllum L. (twoleaf nightshade), S. jamaicense Mill. (Jamaican nightshade), and S. torvum Sw. (turkeyberry).

Category I invasive exotics are defined by the FLEPPC as those plants that alter native plant communities by displacing native species, changing community structure or ecological functions, or hybridizing with natives. The FLEPPC defines Category II invasive exotics are those that have increased in abundance or frequency, but have not yet altered Florida plant communities to the extent shown by Category I species.

As members of the same genus, the Solanum species identified by the FLEPPC as invasive share certain morphological features. These similarities can lead to misidentification. This publication provides a guide to differentiate the invasive Solanum species, along with information about the ecology and management of each species. Also included is information on another relatively common species, Solanum capsicoides All., which can easily be confused with some of the invasive Solanum species.

Identification and Florida distribution

The five Solanum spp. on the FLEPPC's 2007 List of Invasive Plant Species can be identified using morphological characters and also by the habitat in which they are found. For example, wetland nightshade (S. tampicense) is found in wetlands, whereas the other four species are typically found in more upland, and often disturbed, habitats. Tropical soda apple is found both in open areas with full sun (often in pastures), but also in wooded hammocks. In contrast, Jamaican nightshade is found almost exclusively in or nearby wooded areas.

The following table provides some of the key characters that can be used to differentiate the species, as well as information on the habitats in which the species are found and the counties where herbaria specimens have been collected.

Table 1. Identifying characteristics of FLEPPC Category I and Category II Solanum spp. and S. capsicoides

Table 1 Page 1. 

Table 1 Page 2. 

Table 1 Page 3. 

Native Distribution

The five Solanum spp. on the FLEPPC 2007 List of Invasive Plant Species are native to Mexico, Central America, South America, and/or the Caribbean.

Experts do not agree on the native range of S. capsicoides. Some consider the plant to be a native in Florida (Wunderlin and Hansen 2008) while others believe it is native to the Caribbean (D’Arcy 1974) or to eastern Brazil (Wagner et al. 1999). Regardless of the origin of S. capsicoides, it is not considered to be invasive in Florida. Native and exotic ranges for the invasive species are indicated in Table 2.

Control Measures

Prior to taking action to control a suspected invasive plant, verify that the plant is an invasive and not a native species. Species verification can be obtained from a local Florida Cooperative Extension Service office (http://solutionsforyourlife.ufl.edu/map/).

Chemical

Solanum tampicense. Herbicides that have shown the most promise in controlling this species include glyphosate, 2,4-D, and triclopyr. Seeds buried in the soil have been found to maintain their viability for as long as five years. As such, follow-up site scouting of treated areas and additional treatments of newly germinated plants may be necessary (Langeland and Stocker 2001).

Solanum viarum. Based on research conducted by Ferrell and Mullahey (2006), heavy infestations of tropical soda apple are best controlled by herbicides, such as Milestone or ForeFront. Aminopyralid is the active ingredient for both of these. Field research has shown that herbicides containing this particular active ingredient have been successful at not only postemergence control of tropical soda apple, but preemergence control of germinating seedlings more than six months after the initial application.

The following application rates for each herbicide are label rates for rangeland/pasture/open space with dense infestations: 1) Milestone, 5-7 oz./acre in at least 20 gallons of water per acre; 2) ForeFront R&P, 2-2.6 pints/acre in at least 20 gallons of water per acre.

A mowing regiment is not required when using these herbicides, but best results are obtained with the use of a non-ionic surfactant (0.25% v/v) in the spray mix. Herbicides effective for spot spraying include Remedy or Forefront, mixed at a 0.5% solution, or Milestone at 0.5 to 0.8 oz per 2.5 gal (15 - 20 ml per 2.5 gal). Consider adding 0.25% non-ionic surfactant and a color marker to the herbicide solution to help identify plants that have been treated. It is also recommended that application of sprays is before budding/early flowering if possible. For more, see EDIS Publication SSAGR77, Tropical Soda Apple: Biology, Ecology and Management of a Noxious Weed in Florida, http://edis.ifas.ufl.edu/UW097.

A triclopyr formulation labeled for tropical soda apple is Remedy Ultra. Mowing is required to obtain best control of tropical soda apple in Florida when using this herbicide. Old infestations and/or newly germinating patches must be mowed regularly (every 50-60 days through April) to control budding and flowering. A broadcast treatment of 1 quart in 40 gallons of water/acre is recommended 50-60 days after the April mowing (late May-June). Follow-up with spot treatments (1-1 ½ gallons of Remedy Ultra in 100 gallons of total spray mixture) of remaining plants or newly germinated plants.

Solanum jamaicense/Solanum diphyllum. No research has been conducted on chemical control methods for either of these plants. Control methods developed for tropical soda apple (Solanum viarum) may be tried (see above) on these plants.

Solanum torvum. Control of turkeyberry has been achieved chemically on the Hawaiian Islands, where the plant has been found to be susceptible to translocated herbicides, such as glyphosate (Swarbrick 1997).

Biological

Solanum viarum. In early 2003, the South American beetle, Gratiana boliviana (Coleoptera: Chrysomelidae) was released in Florida for biological control of tropical soda apple. Since then, more than128,000 beetles have been released in 19 counties in Florida. In addition, this beetle has been released in Georgia, Alabama, South Carolina and Texas. The beetles are well established in Florida and causing considerable damage to tropical soda apple populations (20-100% defoliation). Beetles move from 1 - 10 miles each year, depending on available food source and initial population size (Medal et al. 2006)

References

D’Arcy, W.G. 1974. Solanum and its close relatives in Florida. Annals Missouri Botanical Garden 61: 819-867.

Sellers, Brent, Jay Ferrell, J. Jeff Mullahey and Pat Hogue. 2006 and 2009. Tropical Soda Apple: Biology, Ecology and Management of a Noxious Weed in Florida. EDIS Publication SS-AGR-77, available at http://edis.ifas.ufl.edu/UW097. Agronomy Department, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL.

FLEPPC. 2007. Florida Pest Plant Council Invasive Species List, 2007. Available at http://www.fleppc.org/list/07list_ctrfld.pdf.

Hickman, J. C. (Eds.). 1993. The Jepson Manual. University of California Press, Berkeley, CA. 1068 pp.

Langeland, K. A., and K. Craddock-Burks. (Eds.). 1998. Identification and Biology of Non-Native Plants in Florida’s Natural Areas. University of Florida, Gainesville. 130-135 pp.

Langeland, K. A. and R. K. Stocker. 2001. Control of Non-native Plants in Natural Areas of Florida. EDIS Publication SP242, available at http://edis.ifas.ufl.edu/WG209. Department of Agronomy, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL. 34 pp.

Medal, J., W. Overholt, P. Stansly, L. Osborne, A. Roda, J. Chong, R. Gaskalla, E. Burns, K. Hibbard, B. Sellers, K. Gioeli, S. Munyan, D. Gandolfo, S. Hight, and J. Cuda. 2006. Classical Biological Control of Tropical Soda Apple in the USA. EDIS Publication ENY-824, available at http://edis.ifas.ufl.edu/in457. Entomology and Nematology Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.

Mullahey, J. J. 2003. Tropical Soda Apple: A Short Summary on the Biology and Description of S. viarum. Available at http://tsa.ifas.ufl.edu.

Swarbrick, J.T. 1997. Weeds of the Pacific Islands. South Pacific Commission, Noumea, New Caledonia.

USDA/ARS. 2006. Germplasm Resources Information Network (GRIN). http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?101505.

Wagner, W.L., D.R. Herbst, and S.H. Sohmer. 1999. Manual of the Flowering Plants of

Hawai'i. 2 vols. Bishop Museum Special Publication 83, University of Hawai'i and Bishop Museum Press, Honolulu, HI.

Wunderlin, R. P. and B. F. Hanson. Atlas of Florida vascular plants. 2008. Institute for Systematic Botany, University of South Florida. Available at http://www.plantatlas.usf.edu/.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, Dean.

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